The present invention relates to a fastening assembly for mechanically attaching a flexible membrane to a roof construction. More particularly the present invention relates to a unique fastening assembly that provides for the attachment of a flexible waterproof membrane to a roof construction at spaced locations and that enables an efficient, durable, waterproof roof system to be obtained.
The use of flexible membranes in roof constructions which include a base or deck having insulation material placed thereon and a waterproof flexible membrane fixed over the insulation have heretofore been available in several different applications. One such application is the securement of the waterproof flexible membrane to the underlying insulation material and roof deck by fully adhering the underneath surface of the membrane by a bonding adhesive to the insulation material. However, such a roof system is somewhat expensive to apply because of the labor intensive requirement of the spreading of an adhesive over the entire roof surface and then adhering the flexible membrane thereto.
Another form of roof system employing a waterproof flexible membrane known heretofore is the use of ballasted material therewith wherein small rocks are deposited over the membrane as placed over the insulation material, the small rocks providing sufficient weight for retaining or anchoring the membrane in its position over the insulation material. Here again, certain disadvantages are present in such a system since the ballast material not only is not cost efficient to utilize, but the weight of the ballast material is oftentimes too great for a roof construction to carry, particularly if the roof construction was not originally designed to receive the additional ballasted weight thereon.
A system that was designed to avoid the problems experienced with the fully adhered membrane and the ballasted membrane in a roof construction was the intermittently attached system. Such systems fall into basically two categories, one being the spot-bonded system as represented by U.S. Pats. Nos. 4,162,597 and 4,389,826 to Kelly and the German Pat. No. 23 00 798. The first Kelly patent, U.S. Pat. No. 4,162,597, relies solely on the attachment of the membrane to a plurality of spaced apart pads by a bonding adhesive, the pads being secured to the insulation and deck through a fastener element. The German patent also fixes a plurality of plates in overlying relation on insulation and then adheres a flexible membrane to the plates by an adhesive or by heat sealing. Although both the Kelly and German patents show systems that have been utilized commercially, both such systems rely upon adhesives or heat sealing to attach the flexible membrane to a plurality of spaced apart pads or plates, and on occasion the adhesive or heat seal in these systems will be affected by temperatures and time and will lose their adhesive qualities, thereby resulting in a failure of the roof system. The other U.S. Pat. No. 4,389,826 to Kelly shows an alternative form of spot bonding system, wherein the membrane is secured over insulation and to a deck by a plurality of spaced apart fasteners that extend through plates and the membrane. Such a system is inherently defective, since the overlying cover member will not always seal the fastener that extends through the membrane, and this system has not found favor in the trade.
The second category of systems that have been developed for intermittently attaching a flexible membrane to a roof construction, is illustrated in the German Pat. No. 28 04 962. The roof system as illustrated in this latter German patent provides for the mechanical spot fastening of the membrane to the underlying roof deck, and for this purpose the German patent includes a post that is fixed to the insulation and over which the flexible membrane is placed. An attachment element with flexible tines formed thereon is provided for forcing the membrane over the post to secure the membrane in place. A cover or cap is then placed over the attachment element. Although this latter system initially functioned to mechanically secure the membrane in place, it was found to be inoperable after a period of use, since the attachment element tended to fracture or rupture the membrane, thereby causing the roof system to fail.
Other patents of which applicant is aware and that are of general interest relative to the subject invention are the U.S. Pat. Nos. 3,426,412 to Streng et al,; 3,453,794 to Block, and 4,382,353 and 4,441,295 to Kelly.
As will be described hereinafter, the subject invention avoids the problems as set forth hereinabove and provides for a relatively simple, inexpensive, and effective mechanical fastening assembly by which a waterproof flexible membrane is attached to a roof construction at spaced apart intervals.